Depolymerization of olefin polymers



Aug. 28, 1945. u. FRANKLIN ETAL DEPOLYMERIZATION OF OLEFIN POLYMERSFiled oct. 1:5, 1941 :s sheets-sheet 1 Pmi Naw QZHAomr ALIII LESLIEU-TRANKLIN N U D M. y m W, E

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Aug- 28, 194.5. L ;u. FRANKLIN EI'AL 2,383,542

DEPOLYMERIZATION OF OLEFIN lPOLYMERS Filed oct. 15. 1941 s sneet-sneet 2VOLUME PER CENT 5&.1API GASQLI EN v\v l o p LQ- "lo Lo v o IlwLslw-xisgawnyl :wnfmo l OJ A n y 3mm/views LESLIE UFRANKLIN 'R EDWARDE. DUNLAY Aug. 28, l1945. u. FRANKLlN ETAL 2,383,642

DEPOLYMERIZATION 0F OLEFIN POLYMERS 'I :s she-ets-sheet s mzowm@ HnmmhmHlm@ Mw@ @2340 er S Filed 061;. 13, 1941 aQznNn) 1mm summing www@ 2 "Kai3mm/1m6- L-SLIE U. FRNKLN EDWARD EDUNLY Patented Aug. 28, 1945nErotYMmlzATroN oF oLEFrN routines Leslie U. Franklin and Edward E.nanny. Port Arthur, Tex., asslgnors to Guit Oil Corporation. Pittsburgh,Pa., a corporation of Pennsylvania Appueanon october 1a, 1,941, serialNo. 114.898

(ci. 19e-.5` o) 5 Claims.

This invention relates to'the depolymerization of olen polymers; and itcomprises a method of depolymerizing olefin lpolymers to producegasoline wherein an olen .polymer of selected gravity is contacted withan adsorbent earth type of catalyst at a temperature suiiicient to'cause substantial depolymerization of the polymer to gasoline butinsufficient to cause substantial cracking of the polymer, separatinggasoline, and then contacting the residual polymer with the same or a.similarcatalyst at a higher temperature;

Y all as more fully hereinafter set forth and as claimed.

It is known that the olens, particularly the lower oleilns such asethylene, propylene, the butylenes and the amyienes, may be converted touseful products by polymerization, thermally or by contact with acatalyst such as phosphoric acid,

sulfuric acid, aluminum chloride, or fuller's earth. The polymerproducts, depending -upon the conditions of polymerization, such as thecatalyst and temperature and time of contact employed,

' vary from light oils boiling in the gasoline boiling point range tovery viscous, almost solid hydrocarbons. Insofar as the polymerizationproduces low boiling motor fuels of the type represented bydiisobutylene (the dimer of isobutylene), the process of oleilnpolymerization is useful in producing gasoline and the like from thelower oleflns. However, polymerization to such a degree is diiilcult,requiring closecontrol of conditions and even so a considerable amountof polymer is produced which boils above the gasoline boiling pointrange. Thus, in the polymerization of isobutylene in the presence ofsulfuric acid, some tri-is0butylene is usually formed along with thedesired di-isobutylene. When aluminum chloride is employed as thepolymerization catalyst, it is difilcult to control the polymerizationso as to produce anything but high boiling polymers.

We have found that olefin polymers boiling above the gasoline boilingpoint range but which are not heavier than albout 25 A. P. I. gravity,can be advantageously converted intogasoline boiling range material by aprocess of depolymerization wherein said olefin polymer, not heavierthan about 25 A. P. I. gravity, is contacted with an adsorbent earthtype of catalyst at a temperature sumcient to cause substantialdepolymerization but insufficient to cause swbstantial cracking,withdrawing gasoline, and further contacting the higher boiling,residual oil with such a catalystfat a higher temperature to producemore gasoline.

There is accomplished by the method of the present invention a,repression of cracking and a promotion of depolymerization, and anaccompanying increase in the yield oi.' gasoline, by con` ducting theearly stage or stages oi the polymer conversion at temperatures whichcause essentially depolymerization without a, substantial amount ofother reactions, separating the gasoline so formed, and furtherconverting the residual oil at a higher temperature. By the term"depolymerizatiori"v as used herein and in the claims we mean that typeof reaction which consists essentially of a. conversion of olen polymerto the original oleflns and lower polymers thereof, whereas by the termcracking" we mean a more fargoing, complex type of reaction leading toother products than the original oleilns and their lower polymers. e

In an advantageous embodiment of the present invention, thedepolymerization is carried out in distinct, successive stages, eachsucceeding stage being carried out at a. higher temperature than' thepreceding stage, and with separation of gasoline boiling range productafter .each stage and before the next.-

` In another embodiment of the invention, a continuous depolymerizationis eiected in contact with the same body of catalyst. but withcontinuous separationof gasoline and progressive increase of thetemperature. This embodiment of the invention may be carried out, forexample,

by heating a charge of polymer with a clay catalyst or the like,continuously distilling or! gasoline, and gradually raising thetemperature. It

The oleiin polymers used in accordance with f the invention may be thoseproduced thermally or by the use of one or more of a variety of poly'-merizing catalysts, such as phosphoric acid, sulfuric acid, aluminumchloride or bromide, zinc chloride, boron fluoride, and fullers earth.Also,

the polymers used in accordance with this invention boil above theygasoline boiling point. range but are not heavier than about 25 A. P. I.gravity.

They are liquid, not viscous semi-solids, at nor V mal temperatures andthey have viscosities and average molecular weights characteristic ofkerosene to somewhat heavy lubricating oil, inclusive.

We have found that oils of such character, such as those produced by thepolymerization of lower oleflns, advantageously a mixture comprising twoor more Ca t0 C oiens, in the presence of aluminum halides, are unstabletoward heat, especially in the presence of adsorbent earth types ofcatalyst, and are much better-suited for; conversion to gasoline thanare heavier more viscous oils sometimes produced by such polymerization.

2' -V Moreover the gasoline thusproducedr is oi high quality.

As an example ofl how olefin polymers suitable for the purpose of theinvention may be prepared, a cracking still gas consisting principallyof C: and C4 hydrocarbons and containing substantial quantities of Caand C4 oleilns is intimately contacted, under a pressure suilicient toliquefy the hydrocarbons, with anhydrous aluminum chloride at atemperature oi! 50 to 150 F. for a time sumcient to produce an oilhaving an A. P. I. gravity oi.' about 25 to 45, advantageously 29 to 43.

We have found that superiorA results are obs A tained by converting theoily polymers thus pro-AA duced by contact with an adsorbent earth typecatalyst at about 550 to 950 F. Such catalysts and such rangeoi-temperature result in an optimum combination oi yield and quality ofproduct and economy of operation. Examples of suitable adsorbent earthtype catalysts capable o! use in accordance with the invention arenatural, coarse fullers earth type clays; impregnated fullersv earth;raw,`ne mesh contact clays; and activated, ne mesh contact clays. 1 Oneof the most economically attractive of such catalysts is a dry,`

16/30 mesh, natural fullers earth type of clay which is marketed underthe `trade name of Superior Clay."

We have also found that acid-treated clays, that is clays contacted withand leached by a strong mineral acid such as HCl or H2504, produce thebest results. Forexample, a per cent aqueous solution of HC1 or H1804 isallowed to percolate down through a bed of clay, such as Superior Clay,and the clay is then dried and screened to 16/30 mesh size.

Pressures above atmospheric maybe employed in my depolymerizationprocess, and the depolymerization to lower boiling oil may b@ carriedout in? the liquid phase, but we have found that best results areobtained when approximately atmospheric or lower pressures and vaporphase conversion oi the oil are used. Greater yields of `gasoline arethus obtained. As used in the speci- `iication and claims, however, theterm contacting hydrocarbon oil with an adsorbent-earth typeoicatalyst," or equivalent expressions, when unqualified, are intendedto include contact of the oil vapor or liquid oil, or both, with thesolid catalyst.

Advantageously, in the depolymerization, there is recycled to the zoneof depolymerization a part of the low boiling or gaseous olefinsproduced by the depolymerization. The yield of gasoline boil- Ing rangematerial is thereby increased.

The invention will be further illustrated and better understood byreference to the accompanying drawings. In the drawings,

Fig. l is a diagrammatic representation of an advantageous embodiment ofthe invention;

Fig. 2 is a graph showing improvements obtained by blending the gasolineproduct of the invention with a low antilmock gasoline; and

Fig'. 3 is a graph showing blending values of the gasoline product ofthe invention.

Referring' to Fig. 1, arf olefin polymer of 25 to 45 A. -P. I. gravityproduced as described above is pumped through a. line I by a pump 2-intoa conversion zone 3 containing an acid treated clay suitably disposedtherein and maintained at about 800'.' to 900 F. and atmosphericpressure or lower. The oil is first heated therein to 300'to 900 F. andthen contacted with the clay, thereby causing conversion into lighterproducts. The conversion products and unconverted oil are passed aseaeaca through a line I into a flash chamber or separator l wherein ,themixture is cooled and a rough separation of normallygaseous'hydrocarbons irom normally liquid hydrocarbons is effected. The5 gases are removed through a line l and the liquid is removed andpumped through'a line 'I' by a pump 8 into a fractionating column II. Y

nractionating colu'mn Il, the oil-is fractionated into a normallygaseous traction (removed through a line I2). alight gasoline fraction(above about '15 API gravity, and removed tnough a valved une n), aheavier gasoline vfraction (about 50 to 70 API gravity, and removedthrough a line I4), and a bottoms (removed through a line l5). The gasfraction removed from column II through line I2, and the gas removedfrom separator 5 through line E, are conducted to a header I6 by controlof which any desired portion of the gas may be recycled to conversionzone 3 through a line 20 by means ofpump 2l or removed from the systemthrough a line 22. Part oi the light gasoline fraction removed fromcolumn II through line I3 may be diverted through a'valved line 23 andintroduced into line 20, thus being recycled to conversion zone 3.Additional olenic material may be introduced through a line 24 into therecycle stream to zone 3.

Any desired portion of the bottoms removed from column I I through lineI5 may be removed fromthe system through avalved line 25 or pumpedthrough a valved line 2B by a pump 21 back into conversion zone 3.Advantageously, however, all of the bottoms removed from column il ispassed through a, valved line 28 to a second conversion zone 30, whichis similar to conversion zone 3 but is maintained at a substantiallyhigher j-temperature, advantageously about 950 to 1100 F. The bottomsfrom column II is iirst heated therein to 950 to 1100 F. and then passedtherethrough in contact with ran acid treated 'clay catalyst, therebycausing conversion of the oil to lighter products. The conversionproducts and unconverted oil are passed through a line 32 into a iiashchamber or separator 33 wherein a rough separation of normally gaseousfrom.

normally liquid hydrocarbons is effected as in separator 5. The gasesare removed through a line 34 and the liquid is removed and pumpedthrough a line 35 bya pump 36 into a fractionating column 3l.

In fractionating column 31, as in column II, the oil is fractionatedinto a normally gaseous fraction, a light gasoline fraction (above about75 API), a heavier gasoline fraction (about 50 to 70 API), and abottoms. These fractions are removed from column 43l through the lines40, 4I, 42 and 43, respectively. The gas fraction removed through line40, and the gases removed from separator 33 through line 34 areconducted to a header 44 by control of which any desired portion of thegas may be recycled to conversion zone 30 through a line'45 by means ofa pump GB or removed from the system through a. line 41.' Part' of thelight gasoline fraction removed from column 31 through line 4| may bediverted through a valved line 50 and introduced into line 45, thusbeing recycled to the system. Additional olefinic material may beintroduced through a line 5I into the recycle stream to zone 30. andprovided with a two-way pump. 53 connects recycle line 20 of the rststage conversion with 7.5 recycle line 45 of the second stageconversion.

A connecting line 52 containing a valve` By the use of valved line 52and pump 53, a pore tion of the gas recycle to zone-3 may be diverted tozone 30 or a portion of the gas recycle to `zone 30 may be diverted tozone 3. The bottoms removed from column 31 through line 43 is in partremoved from the system through a valved line 54 and in part is pumpedthrough a valved line 55 by a pump 5B back to zone 30.

In the practice ofthe embodiment of the invention described above withreference to Fig. 1,

- in the first stage polymer conversion (zone 3) a greater degree ofdepolymerization and a smaller degree of cracking' occurs than in thesecond stage polymer conversion (zone 30). because of the highertemperature prevailing in zone 80. Ifdesired, three or even more stagesof conversion may be employed, the gasoline-free bottoms from eachprecedingy stage being converted in the next stage Aat a highertemperature. We have found, however. that twoor three-stagevconversionis most advantageous.

The following specific examples will further serve to illustrate -thepractice and the benefits of the invention:

Eample 1.-To a vessel provided with a, stirrer and means for temperaturecontrol were charged 1730 parts by weight of a liquefied cracking stillgas and 1 part by weight of anhydrous aluminum chloride. The crackingstill gas tested as follows (volume per cent, gas basis):

The stirrer was started and the temperature was maintained at about 90F. .A pressure oi 80 pounds per square inch gauge was initiallymaintained in the vessel to liqueiy the reactants, but this pressuredropped during the subsequent reaction to about 25 pounds. Anhydrousaluminum chloride was added in portions of 1 par-t by weight every 2hours un-til, after about 30 hours, a sample of gas taken from thevessel was found to contain substantially no unsaturates. In all, 17parts by .weight of aluminum chloride were added. The vessel was thenopened and normally gaseous, hydrocarbons, containing only 1.5 per centof unsaturates, were removed. A liquid polymer productv amounting toalmost 100 per cent by weight on the olefins in the charge and testingas follows, was left as residue:

Gravity API 35.1 Viscosity: SUV:

100 F 811 210 F 81 Viscosity index 100 Flash, OC F l220 Fire, OC F 285Pour -F below -25 Color, Saybolt +8 Sulfur, B per cent 0.02 Chloride do0.02 Acid heat F 4 Iodine No., Mod. Hanus 60.7 Neutralization` NoNeutral Aniline point F 261.1

The above liquid polymer was passed through a bed of acid treated20/30\mesh No. V2 Superior Gas analysis l Per cent by volume of gas H2and CH: 8.94 Ethylene 2.48 Ebbene ,3.88 Propylene 12.50 Propane 5.28Isobutylene 46.66 n-Butylenes 7.33 Butanes 7.33 Pentanes l4.31 Hexanesand' higher hydrocarbons 1.29

Total 100.00

Liquid analysis Gravity API 62.9 'Color'. NPA 2.5 Acid heat F 158Distillation, gasoline:

Over point F 93 End point ..F 635 10% at F 131 50 316. Recovery percent-- 83 Residue do Loss do 14 40per cent propylene.

Clay maintained at about 840 F. and was main-` tained at atmosphericpressure. The ratio of clay to total charge was 0.226 pound of clay pergallon of charge. A contact' time of 9.7 seconds was maintained. By thistreatment, 7.8 per cent by weight of the charge wasconverted to normallygaseous hydrocarbons and the remainder to a liquid, testing,respectively, as follows: l

The above liquid was debutanized, the overhead containing 71 per centbutylenes and 10 The debutanized bottoms was fractionated into agasoline fraction and a heavier oil fraction. The gasoline fraction,amounting to 73 per cen-t by weight of the debutanized bottoms (61 percent by weightvof the olens charged to the polymerization process),tested as follows:

Gravity API 62.0 Doctor Good Sulfur. L per cent 0.02 chloride do 0.03Acid heat F 160 Iodine No., Mod. Hanus 248 Octane No., CFR-ASTM 78.0Octane blending-value (in of 44.0

octanestock) 111.0 Distillation, gasoline:

Over point F 109 End point F 406 10% at F 150 50 249 1 365 Recovery'----per cent-- 98 Residue do 1 Loss do 1 The heavier oil fraction ofthe distillation described above amounted to 21 per cent by weight ofthe debutanized bottoms. It had an API gravity of 40.3 and adistillation range of 444 to 686 F. This 40.3 API fraction was submittedto further conversion by passing it through a bed of acid treated 16/20mesh No. V2 Superior Clay main-tained at a temperature of about 1015othe contact time and clay-to-charge ratio lon of charge, respectively.Gas'equal to 35 per cent by weight of the charge and a liquid equal to62 per centl by weight of the charge were thus obtained, testing,respectively, as'follows:

Gas anali/sis 54 1 v.A P I mimgzml oc e o.A

Base SPW-k1 gasoline (ora-ASTM method) (l) Cracked gasoline from Gul!10%oiblend. 06.0to68.0=2.0 Coastnlcrude. A (2) Cscked gasolinefromRodessa do..-. 62.0 to 83.8=l.8

cru e. (3) Cracked gasoline from West -..do 60.3to 67.0=l.3

Texas crude. (4) Straight run gasolinefrom -.-do 54.6to60Jb4A East'iexas crude. j (5) Straight run gasoline from -.do 53.0 to 67.3=4.3

West Texas crude. (6) 50 per cent straight run and do 58.0to02.0=4.0

50 per cent cracked gasoline (per cent by volume). A

Per cent by volume -of gas Acid gas (HzS Orsat) 0.52 Methane 39.04Ethylene 10.91 Ethane 13.33 Propane v 5.35 Propylene 13.64 YIsobutylene5.25 n-Butylene 4.20 Isobutane, n-butane 3.40 Pentane and heavier.Y 4.72

Liquid analysis Gravity I 2API 42.6 Sulfur, L per cent-- 0.01 Chloridedo 0.03 Acid heat F 104 Iodine No.; Mod. Hanus 115.4 Distillationgasoline:

Over `point F 104 End. point F 646` 10% at F 173 50 4--- 440v 90V 605Per cent at 392 F 41 Recovery per cent-- r 92 Residue do 1 Loss do '7.

Vori fiaouomnion,i the above liquid yielded 44.5

per cent by weight of gasoline and 52 per cent by weight of bottoms,percentages being based on liquid charged to the still. The bottoms hada boiling range of 462 to 673 F. and the gasoline tested as follows:

Example 2.-The 54.1 API gasoline whose analysis is set forth in the lastparagraph of Example 1 was blended with diilerent low antiknock crackedand straight run gasolinas and with a mixture of straight run gasolineand cracked gasoline. The addition of only 10 per cent by volume of theabove 54.1 API gasoline produced in the blends the following increasesin `octane number, the rst gure in the right-hand' column being theoctane number of the base stock, the second figure being the octanenumber In Fig. 2 is shown graphically the results ot blending variousamounts, up to 70 per cent by volume on the blend, of the 54.1API'gravity gasoline of Example 1 with the 50-50 volume mixture ofstraight run and cracked gasoline referred to above (No. 6 in the abovetable). In this figure, abscissae represent percentages by volume of54.1 API gasoline in the blend and ordinates represent octane numbers(CFR-ASTM method). The bottom curve represents blends without addedtetra-ethyl lead and the upper curves represent blends with variousamounts of added tetra-ethyl lead, as shown.

In Fig. 3 are shown the blending valuesof the 54.1 A. P. I. gasoline ofExample 1 with the 50-50 mixture referred to above (No. 6in the abovetable). In this figure, absclssae represent percentages by volume of the54.1 A. P. I. gasoline in the blends and` ordinates represent the octaneblending values (CFR-ASTM) of the 54.1 A. P. I. gasoline. These octaneblending values are derived by a Well known method, being calculatedfrom the known octane number of the base stock (50-50 mixture) and theknown octane number of the blend on the assumption that the octanenumber of the added' gasoline is proportional to its amount and to itsoctane number. Suchoctane blending values are a criterion of the efofthe blend, andthe third gure being the difference in or increase ofoctane number due to 10 per cent of the added gasoline:

vfectiveness of high octane gasolines for blending purposes. As is'evident from Fig. 3, the gasoline product 0f the invention has a veryhigh blending value when used in small amounts; it has the apparenteiect when used in small amounts of a very much higher octane numbergasoline. l

While the invention has been described with A particular reference tocertain embodiments and specific examples, it is not limited to suchembodiments and specificl examples except as defined in the appendedclaims. What we claim is: 1.A A method of depolymerizing olen polymerswhich comprises contacting an olen polymer of about 25 to 45 A. P. I.gravity with an adsorbent earth type of catalysthrst at a temperaturesuf.

cient Jto cause substantial depolymerization of the polymer togasolinebut insufficient to cause arno method of claim 1, 'wherein tiretom-d perature at which the polymer is rst contacted with catalyst isbetween about 550 and 950;E.

4. Amethcd of producing gasoline, which oomprises contacting an olenpolymer of about 25 to 45 A. P. I. gravity with an adsorbent earth typeof catalyst at a temperature `between about 550 and 950 F. suilicient todepolymerize asubstantial` amount o! the polymer to gasoline ,boilingrange hydrocarbons without substantial mer to gasoline boiling rangehydrocarbons with- Vout substantial cracking, separating from theproduct of depolymerization a lower oleiin trac.

tion and a gasoline boiling range fraction, recycling to said contactingzone, together with further quantities of said olen polymer, a portionof said lower olen fraction, and contacting the higher boiling residueof depolymerization product and undepolymerized polymer with anadsorbent-earth type of catalyst at a temperature between about 950 and1100 F. to further depolymerize it and so produce more gasoline boilingrange hydrocarbons, and separating gasoline boiling'range hydrocarbons.

LESLIE U. FRANKLIN. EDWARD E. DUNLAY;

